1. Field of the Invention
The present invention relates to an air vent structure for an inner air discharge of a helmet adapted to protect a user""s head when a user rides a motorcycle, and in particular to an air vent structure for a helmet which is capable of preventing a breath steam from forming in an inner surface of a shield by installing an air vent in lower both sides of a shield installed in a front side of a helmet and accurately adjusting an opening and closing degree of an air vent.
2. Description of the Background Art
Generally, when a person rides a two-wheeled vehicle, the person must wear a head protecting helmet for protecting a rider""s head. In the case of a full face helmet which covers up to a jaw portion of a user, a front shield must be installed.
The above shield is capable of preventing any interference in a field of vision by a wind force which occurs when a vehicle runs in a certain direction and preventing a breathing difficulty and obtaining a warm keeping effect in the winter season.
However, since the conventional helmet having a shield does not have an air vent for discharging an inner air to the outside, there are the following problems.
Namely, when a shield is dropped down for thereby shielding a forward field of vision of the helmet, the shield is capable of preventing a wind which is flown in a running direction and overcoming a breathing problem. However, in the case that there is a big temperature difference between the inner side and outside of the helmet like in the winter season, a breath steam may be formed in an inner surface of the shield due to a user""s breathing, so that the user""s field of vision becomes bad.
In addition, in order to overcome the above problems, various air vent ways are developed for thereby discharging an inner air to the outside. As one of the ways, the applicant of the present invention filed a patent No. 10-0299319(hereinafter, it is referred to as Prior art).
As shown in FIGS. 1 and 2, there is prepared a helmet body 10 which has a padding 12 in the interior of the same and a shield 20 in a front opening portion 11. At the both front sides of the helmet body 10, a communicating hole 13 is formed in the padding 12, and a groove 14 is formed in such a manner that the communication hole 13 is positioned in the center.
In addition, an air vent member 30 is installed in such a manner that the air vent member is closely fixed to the groove 14, and one end of the same is fixed by an engaging shoulder portion 31, and the other end of the same is engaged by an engaging unit 32, and a cover portion 33 is formed thereon for thereby forming a communicating portion 34.
According to the above described prior art, the air which flows from the front side to the side of the helmet body 10 flows along an inner side of the cover portion 33 of the air vent member 30, namely, along the inner side of the communicating portion 34 for thereby sucking an inner air of the communication hole 13 and discharging the sucked air(based on Vernoulli""s theorem for a fluid).
However, in the air vent structure of the above prior art, the air is guided to flow in an inner side of the cover portion of the air vent member. There is provided only an opening and closing portion for opening and closing the guide portion. Therefore, when discharging an inner air, the amount of the air discharged is not controlled.
In detail, the size of the communicating hole 13 and the cross sectional area of the communication portion 34 are fixed, namely, unchangeable, the amount of the air flowing along the communicating portion 34 is constant. Therefore, the amount of the inner air discharged through the communication hole 13 is constant.
In the case that the formation of the breath steam is increased in the shield, the discharging amount of the air is not increased. In addition, in the case that the formation of the breath steam is small, it is impossible to decrease the discharging amount of the air for keeping warm.
Accordingly, it is an object of the present invention to provide an air vent structure for a helmet which overcome the problems encountered in the conventional art.
It is another object of the present invention to provide an air vent structure for a helmet which is capable of discharging an inner air based on the flow of an air of an air vent by installing an air vent at both lower sides of a shield of a helmet, improving a structure of an air flow of an air vent and accurately adjusting the amount of flowing air, and it is possible to adjust the flowing amount of air based on a helmet user""s condition and a state of an inner and outer side of a helmet for thereby implementing a pleasant state.
In order to achieve the above objects, there is provided an air vent for a helmet which includes a helmet body which includes a front opening portion, a shield installed in such a manner that the opening portion is openable, a pad provided in a whole inner surface, and a communicating hole which is formed at right and left sides of a jaw protection portion in a lower portion of the opening portion and communicates with the outside; a base member which is fixed in such a manner that an outer portion of the communicating hole of the helmet body is covered, and which includes a first air inlet hole formed in a front side of the helmet, a first air moving space portion formed from the first air inlet hole to a rear side, a second air inlet hole formed in such a manner that more air is flown into the first air moving space portion, and a plurality of first air outlet holes formed in a rear side of the air moving space portion; a door base member which is slidable on the base member in a forward and backward direction in a state that a first inward rim closely is contacted with an outer surface of the base member and the first air inlet hole is opened and closed by a first end portion opens during the sliding, and which includes a third air inlet hole formed in an inner side of a first end portion and a second air outlet hole formed in a rear side at a certain distance from the third air inlet hole; and a side door member which is slidable on the door base member in a forward and backward direction in a state that a second inward rim is closely contacted with an outer surface of the door base member and the second air inlet hole is opened and closed by a second end portion during the sliding, and which includes a second air moving space portion in a rear side.